The present invention relates to a silent chain having a large number of interleaved link plates articulately connected by round connector pins in an endless fashion.
Silent chains of the type concerned have guide links and articular links alternately arranged in the direction of the length of the silent chain and they are articulately connected together in an endless fashion by means of round connector pins. The guide links each have a pair of guide plates and at least one guide link plate disposed laterally between the guide plates. The guide plates and guide link plate each have a pair of pin holes spaced in the longitudinal direction of the chain. The articular links each have at least two laterally aligned articular link plates each having a pair of pin holes spaced in the longitudinal direction of the chain, rile number of the articular link plates being one more than the number of the guide link plates. The articular link plates in each of the articular links are interleaved with the guide plates and guide link plates in the adjacent link plate.
In assembly, one of the pin holes, located near a leading end (as viewed in the advancing direction of the chain) of each guide plate of one guide link and one of the pin holes, located near a leading end of the guide link plate of the same guide link are laterally aligned with one of the pin holes, located near a trailing end (as viewed in the advancing direction of the chain) of each articular link plate of the adjacent articular link, and one round connector pin is inserted through the laterally aligned holes in the guide plates, guide link plate and articular link plates, so that the guide links and the articular links are connected together in an endless fashion. The outside diameter of the round connector pin is made smaller than the inside diameter of the pin holes of the guide link plate and articular link plates so as to define a space or clearance between the outer peripheral surface of the connector pin and the inner peripheral surface of the mating pin holes of the guide and articular link plates, so that the adjacent guide and articular links can bend or articulate about the round connector pin when the chain wraps around a sprocket. The round connector pin is press-fitted with the guide plates to avoid unintentional disassembly of the silent chain.
Japanese Patent Laid-open Publication No. (HEI) 11-201238 shows a conventional silent chain, in which the pitch of the guide plates (represented by the distance between pin hole centers in each guide plate) is initially made larger than the pitch of the guide and articular link plates (represented by the distance between pin hole centers in each link plate). After the assembly of the silent chain, the silent chain is prestressed to plastically deform the link plates to such an extent that the pitch of the guide plates and the pitch of the link plates are substantially equal with each other.
However, as shown here in FIG. 8, since the pitch of the guide plates 50 is equal to the pitch of the guide link plates 52, an annular space is defined between the outer peripheral surface of each round connector pin 54 and the inner peripheral surface of the mating pin hole of each guide link plate 52 in concentric relation to the round connector pin 54. With this arrangement, when the conventional chain is subjected to a tensile force, the tensile force in each guide link acts concentratedly on the guide plates 50.
As a result, the guide plates 50 are deformed into a bow-like shape and the round connector pins 54 are bent, as shown in FIG. 9. The amount of deformation of the guide plates and round connector pins may increase until the outer peripheral surface of each round connector pin 54 contacts the inner peripheral surface of the mating pin hole of one guide link plate 52a which is located at the center in the transverse direction of the guide link.
With the outer peripheral surface of the round connector pin being in contact with the inner peripheral surface of the pin hole in the central guide link plate 52a, in the guide links, a tensile force acting on the silent chain is born solely by the guide plates 50 and the central guide link plate 52a. In the articular links, due to the bend or deformation of the round connector pins 54, the tensile force acting on the silent chain is born solely by two outermost articular link plates 56, 56.
The conventional silent chain of the foregoing construction is disadvantageous for the reasons enumerated below.
(1) The round connector pin is susceptible to bending and repeated bending force is likely to cause fatigue.
(2) Due to the bend or deformation of the round connector pin, the pitch of the guide links and the pitch of the articular links are caused to change with the result that the noise produced when the silent chain engages the sprocket increases.
(3) Since, in the guide links, the tensile force acting on the silent chain is concentrated on the guide plates, the guide plates are likely to be damaged or broken.
(4) Due to the bend of the round connector pin, the tensile force acting on the silent chain is concentrated on the central guide link plate, which leads to reduction of the service life of the silent chain as a whole.
(5) The service life of the silent chain as a whole is further cut down by two outermost articular link plates, which are subjected to stress concentration when a tensile force is applied to the silent chain.
(6) with the round connector pin being bent, each individual link plate is more or less subject to stress concentration. When the concentrated stress exceeds the elastic limit of the material of the link plate, the link plate is plastically deformed or otherwise damaged.
It is, accordingly, an object of the present invention to provide a silent chain with round connector pins, which has structural features enabling a tensile force acting on the silent chain to act concurrently and uniformly on the guide plates and the link plates in each guide link.
To achieve the foregoing object, there is provided, in accordance with the present invention, a silent chain comprising guide links and articular links alternately arranged in the longitudinal direction of the chain. Each of the guide links has a pair of guide plates and at least one guide link plate disposed laterally between the guide plates. The guide plates each have a pair of pin holes spaced in the longitudinal direction of the chain, and the guide link plate has a pair of pin holes spaced in the longitudinal direction of the chair. Each of the articular links has at least two laterally aligned articular link plates each having a pair of pin holes spaced in the longitudinal direction of the chain. The number of the articular link plates is one more than the number of the guide link plates. Round connector pins are inserted through the pin holes in the guide plates, the pin holes in ea h guide link plate and the pin holes in the articular link plates so as to connect the guide links and the articular links in an endless fashion with the guide link plates and he articular link plates being interleaved with each other.
The pin holes in each of the guide plates have an inside diameter smaller than an outside diameter of the round connector pins, the round connector pins being press-fitted with the guide plates. The pin holes in each guide link plate have an inside diameter larger than the outside diameter of the round connector pins. The pitch or distance between pin hole centers in each of the guide plates is larger than the pitch or distance between pin hole centers in each guide link plate. Two adjacent ones of the connector pins, inserted through the pin holes in each guide link plate and pressed fitted in tie pin holes in each of the guide plates, have an outside distance substantially equal to an outside distance between the pin holes in the guide link plate.
In a pre-press-fitting state in which the round connector pins are not yet connected by press-fitting to the guide plates, the silent chain of the present invention is constructed to satisfy the expression (1)
Pg+Dg≈Pm+Dmxe2x80x83xe2x80x83(1)
where Pg is the guide plate pitch represented by the distance between pin hole centers in each guide plate, Dg is the inside diameter of the pin holes of each guide plate, Pm is the link plate pitch represented by. the distance between pin hole centers in the guide link plate, and Dm is the inside diameter of the pin holes in the guide link plate.
It is preferable that the left side and the right side of the expression (1) are made physically equal to each other as expressed by the sign xe2x80x9c=xe2x80x9d, rather than nearly equal to each other as expressed above by the sign xe2x80x9c≈xe2x80x9d.
When the round connector pins are press-fitted with the guide plates, the outside diameter of the round connector pins and the inside diameter of the pin holes in the guide plates are changed due to elastic deformation. To optimize the design of the silent chain, the amount of elastic deformations of the round connector pins and guide plates should preferably be considered.
In a post-press-fitting state in which the round connector pins are already connected by press-fitting to the guide plates, the silent chain of the present invention is constructed to satisfy the expressions (2)-(4)
L1≈L2xe2x80x83xe2x80x83(2)
Pgxe2x80x2+Dpxe2x80x2≈Pm+Dmxe2x80x83xe2x80x83(3)
(Pm+Dmxe2x88x92Dpxe2x80x2)xe2x88x92Pgxe2x80x2≈0xe2x80x83xe2x80x83(4)
where L1 is the outside distance between the round connector pins press-fitted in the pin holes in each guide plate, L2 is the outside distance between the pin holes in the guide link plate, Pgxe2x80x2 is the post-press-fitting guide plate pitch represented by the distance between pin hole centers in each guide plate press-fitted with the round connector pins, Dpxe2x80x2 is the outside diameter of the round connector pins press-fitted in each guide plate, Pm is as defined above, and Dm is as defined above.
It is preferable that in each of the foregoing expressions (2)-(4), the left side and the right side are made physically (Equal to each other as expressed by the sign xe2x80x9c=xe2x80x9d, rather than nearly equal to each other as expressed above by the sign xe2x80x9c≈xe2x80x9d.
However, It is difficult to make the left side and the right side of each of the expressions (1)-(4) physically equal to each other. Accordingly, in the silent chain of the present invention, the left side of the expression (4) is preferably made less than 0.5% of the pitch of the silent chain (chain pitch).
The term xe2x80x9cchain pitchxe2x80x9d used herein represents the center distance between the adjacent round connector pins. The term xe2x80x9cguide plate pitch Pgxe2x80x9d used herein represents the distance between pin hole centers in each guide plate before the silent chain is prestressed. Similarly, the term xe2x80x9clink plate pitch Pmxe2x80x9d used herein represents the distance between pin hole centers in each guide link plate before the silent chain is prestressed. The term xe2x80x9cpost-press-fitting guide plate pitch Pgxe2x80x2xe2x80x9d used herein represents the distance between pin hole centers in each guide plate including the amount of elastic deformations caused in the round connector pins and the guide plate due to press-fitting connection.
By thus constructing the silent chain, in each guide link, the round connector pins press-fitted in the guide plates extent straight with their outer peripheral surface being in contact with the inner peripheral surfaces of the pin holes in the guide link plate. When the silent chain is subjected to a tensile force, the tensile force acts on the guide plates and the guide link plate simultaneously. Thus, the round connector pins do not undergo elastic deformation or bending, and the guide plates and the guide link plate (particularly, the central guide link plate when plural guide link plates are used) are completely free from stress concentration.